Surface energy budget variability: A case study over grass with special regard to minor inhomogeneities in the source area

Eddy correlation measurements of surface energy fluxes above a meadow site are presented and discussed in terms of energy balance closure. The degree of closure changed with time and wind direction, which can be explained by temporal and spatial variations of the surrounding vegetation. More frequently than not, a tendency towards an energy "deficit" was observed, that means, the sum of turbulent fluxes was less than the available energy. As a possible reason, we cautiously suggest that large-scale flux components may have to be taken into account. If so, then a convenient way to obtain fairly accurate total surface energy fluxes would be to correct the turbulent fluxes with an appropriate factor that forces the budget to perfect closure. [References: 51